An active matrix organic light-emitting diode (AMOLED) is driven by a current generated by a driving transistor in a saturated state, so as to emit light. In the case that an identical grayscale voltage is applied to the driving transistor, different driving currents, i.e., current unevenness, may occur due to different critical voltages. For a low temperature poly-silicon (LTPS) process, it is impossible to provide the driving transistor with a constant threshold voltage Vth, and meanwhile voltage drift may easily occur for the threshold voltage Vth, so it is impossible for a traditional 2T1C (two transistors and one capacitor)-based pixel driving circuit to provide even brightness. In addition, for the existing pixel driving circuit, the driving current of the driving transistor is related to an on-state voltage of the OLED, and along with the aging of the OLED, this on-state voltage may change too, so the driving current of the driving transistor may be adversely affected by the aging of the OLED.